* [CVE-2026-97539][MODERATE REGULAR] usb: xusbatm: don't rely on id table pointer arithmetic [ Upstream
@ 2026-09-25 18:27 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 18:27 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97539
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: xusbatm: don't rely on id table pointer arithmetic [ Upstream
Commit: fad6cab36474758abf55c6419dd79a06a27fcefc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fad6cab36474758abf55c6419dd79a06a27fcefc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97539
Analysis date: Fri, 25 Sep 2026 14:27:07 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97539 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97539
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE REGULAR
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-97539 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97539 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';CWE-125;CWE-823;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.6';DESCR 'An out of bounds access in the xusbatm USB ATM driver occurs because xusbatm_bind() calculates a configuration index by subtracting a static USB ID table address from the probe ID pointer. When a dynamic USB ID is used the probe ID may be heap allocated and the calculated index can be far outside the driver configuration arrays. This can cause invalid kernel memory reads and may lead to incorrect USB interface handling or a kernel crash. For the CVSS the PR:H because reliable triggering normally requires administrative access to register a dynamic USB ID through the local new_id interface and access to a matching USB device. The issue is not network reachable. The base impact is local denial of service. The paranoid score retains a limited confidentiality and integrity impact because the out of bounds value is consumed by driver logic, but a direct disclosure or write primitive is not demonstrated and requires manual validation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES OOB USB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::
The conservative and paranoid scores are identical. No floor or cap was applied.
2. Signal breakdown
Positive signals:
* +1 Weak indirect corruption concern. The pointer subtraction `id - xusbatm_usb_ids` is invalid when `id` is a heap allocated dynamic USB ID. The resulting `drv_ix` can be far outside the intended static configuration arrays, causing invalid kernel memory reads through `rx_altsetting[drv_ix]`, `tx_altsetting[drv_ix]`, and `rx_endpoint[drv_ix]`.
* +1 Plausible kernel crash or strong DoS. A wildly out of bounds array index can access an invalid kernel address during USB probe and may cause an Oops or crash.
Negative signals:
* -2 Host-admin-equivalent privilege requirement. Dynamic USB IDs are registered through the USB driver `new_id` sysfs control path. Registering such IDs requires host administrative authority, normally CAP_SYS_ADMIN and permission to write the relevant host sysfs attribute.
Important non-awarded signals:
* Controlled reclaim is not demonstrated.
* Arbitrary kernel write is not demonstrated.
* No use-after-free, double-free, refcount misuse, or stale post-lifetime reference is established.
* Confidentiality is not awarded. The patch demonstrates an invalid internal array read, but no path copies the out of bounds data to userspace, the network, or a device-visible interface.
* Integrity is not awarded. The patch does not demonstrate a write through the invalid index or a security-sensitive state modification.
* Remote reachability is not established. USB device matching and dynamic-ID registration are local host operations.
* No local unprivileged trigger is established because the complete dynamic-ID registration step requires host administrative privilege.
* No special hardware penalty is applied. A USB device is relevant to the path, but the issue can concern an already attached matching device and does not require rare hardware.
* No additional availability point is awarded because the potential Oops/crash is the same consequence already counted above.
3. Reachability analysis
The vulnerable path is reached when the xusbatm USB ATM driver probes a device using a dynamic USB ID. The dynamic ID object is allocated separately from the static `xusbatm_usb_ids` table, so pointer subtraction against the static table produces an invalid index.
The required `new_id` operation is a host sysfs driver-management action. It is governed by host administrative privilege rather than a namespace-local networking capability. Therefore, the complete trigger is not namespace-scoped. An unprivileged user in a user namespace, network namespace, or container is not shown to be able to register a dynamic ID for this host USB driver.
A matching connected USB device is also needed for probe execution. The patch does not establish remote triggering, malicious USB-device emulation by an unprivileged local actor, or a way to reach the vulnerable path without host administrative control. There is no race requirement.
4. Primitive and severity interpretation
The exact primitive is an out of bounds array index caused by invalid pointer arithmetic between a heap allocated `usb_device_id` and a static USB ID table. This is not a real UAF despite the patch message link containing `dyn_id_uaf` in its name. The affected pointer is not freed and later reused. Instead, an unrelated heap pointer is incorrectly interpreted as an element of the static ID array.
The subsequent operations read configuration arrays using the invalid index. This is an invalid-read and invalid-state primitive, classified as CLASS_C. The demonstrated or strongly supported consequence is incorrect driver configuration handling and a potential kernel fault during device probing. There is no patch-supported controlled replacement, arbitrary read-back, arbitrary write, callback control, refcount takeover, or privilege-escalation mechanism.
This is not an Important candidate. The issue is operationally relevant for systems using xusbatm and allowing administrative USB driver management, but the complete trigger requires host-admin-equivalent privilege and the patch does not establish meaningful post-crash exploitation leverage. Auto downgrade is allowed because the remaining primitive is a constrained privileged invalid-index crash concern rather than an unresolved active-object lifetime or security-boundary bug.
5. One-sentence report phrase
A host administrator can register a dynamic USB ID that causes the xusbatm driver to calculate an out of bounds configuration index during device probe, potentially resulting in invalid kernel memory reads and a local kernel crash.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm the exact `new_id` capability check and inspect the downstream uses of `rx_altsetting`, `tx_altsetting`, and `rx_endpoint` in the affected kernel version to determine whether all invalid indices fail only through probe-time faults or whether any value can influence an additional memory-access sink.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: usb: xusbatm: don't rely on id table pointer arithmetic [ Upstream
Commit: fad6cab36474758abf55c6419dd79a06a27fcefc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fad6cab36474758abf55c6419dd79a06a27fcefc
Changed files:
drivers/usb/atm/xusbatm.c
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fad6cab36474758abf55c6419dd79a06a27fcefc
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97539 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97539
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS score: 5.6
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: unknown
Paranoid ActionableScore: 0
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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